His remarks come days after the release of an assertive Chinese defense white paper and a blunt reaction from the top Pentagon official, leading to increased fears of a maritime clash between China and the United States.

In a speech Friday to more than two dozen defense chiefs, Prime Minister Lee Hsien Loong called on China and ASEAN members “to break the vicious cycle” by adhering to international law and concluding a Code of Conduct on the South China Sea.

"If a physical clash occurs, which escalates into a wider tension or conflict, either by design or more likely by accident, that would be very bad,: said Lee. "But even if we avoid a physical clash, if the outcome is determined on the basis of might is right, that will set a very bad precedent."

China claims most of the South China Sea and has begun building islands on top of small rocky outcroppings in areas that also are claimed by the Philippines and Vietnam. In all, six governments claim parts of the resource-rich region.

The prime minister delivered the opening keynote address of the Shangri-La Dialogue, which runs through Sunday.

The annual security meeting in Singapore allows countries to discuss "how the tensions in the South China Sea might be better managed and how escalation can be prevented," said Tim Huxley of the London-based International Institute for Strategic Studies (IISS), in a VOA interview. IISS organizes the meeting.

Analysts have interpreted the Chinese military document, issued Tuesday, as a strong warning to Beijing’s Asian neighbors and to Washington about "busy meddling" by the U.S. military in the South China Sea, where
China is intensively building islands.

In a speech in Pearl Harbor, Hawaii, the following day, U.S. Defense Secretary Ashton Carter called for "an immediate and lasting halt" to Chinese reclamation in the disputed waters. He said the American military is "going to meet" the increasing demand for its engagement in the Asia-Pacific region as a result of China’s maritime actions.

Carter, en route to Singapore, told reporters that although the U.S. does not have a territorial claim in the area, "the reason that the United States and everyone else in the region has a stake in this is because it gets to the question of freedom of navigation, freedom of the seas, freedom from coercion, abiding by peaceful and lawful processes."

The new head of the U.S. Pacific Command, Admiral Harry Harris Jr., at his change-of-command ceremony Wednesday in Hawaii, characterized China’s land claims in the disputed waters as "preposterous."

The admiral declared U.S. forces, if called upon, would be ready to “fight tonight to defend American interests in the vast Indo-Asia Pacific. This is not aspirational; it’s in our DNA.”

Carter and Harris are expected to elaborate on their stances when they speak at the Singapore conference.

The senior figure from China is deputy chief of general staff, People’s Liberation Army navy admiral Sun Jinguo.

The four-star officer is leading an 18-member delegation. The admiral, scheduled to address the conference Sunday, is expected to emphasize that China’s rise as a military power is intended to be
peaceful – in line with comments the Chinese have made in past years at this annual conference.

Others in China express a more ominous tone.

"If the United States' bottom line is that China has to halt its activities, then a U.S.-China war is inevitable in the South China Sea," said an editorial Monday in the Global Times, a nationalist tabloid owned by the ruling Communist Party’s official newspaper.

U.S. Defense Department officials confirmed Friday that American surveillance imagery recently detected Chinese military weapons on one of the artificial islands built by China in the Spratley archipelago.

“We were aware of these. But beyond that, in terms of (confirming) any (U.S.) interaction with the Chinese on this you’d have to speak to the State Department,” said Brent Colburn, the top Pentagon spokesman
traveling with the defense secretary.

Although posing no military threat to U.S. ships or planes in the area, the motorized artillery pieces were reported to be within range of an island claimed by Vietnam, on which it has deployed various weaponry for some time.

Meanwhile a video released Friday by the Philippine navy showed Filipino and Vietnamese troops playing games and dancing on the disputed Northeast Cay (also known as Parola island). The 12-hectare island, occupied by the Philippines, is also claimed by Vietnam, China and Taiwan.

The Philippines and Vietnam have recently been seen putting aside their rivalry over competing territorial claims to counter China’s.

The Chinese foreign ministry on Friday denounced the Philippines “illegal” occupation of some islands and reefs and told the United States to act responsibility.

“These type of remarks are not conducive to solving the dispute peacefully and will further damage the region's peace and stability," said Foreign Ministry spokeswoman Hua Chunying at a briefing in Beijing.